Lacustrine, riverine, and spring carbonates are archives of terrestrial climate change and are extensively used to study paleoenvironments. Clumped isotope thermometry has been applied to freshwater carbonates to reconstruct temperatures, however, limited work has been done to evaluate comparative relationships between clumped isotopes and temperature in different types of modern freshwater carbonates. Therefore, in this study, we assemble an extensive calibration dataset with 135 samples of modern lacustrine, fluvial, and spring carbonates from 96 sites and constrain the relationship between independent observations of water temperature and the clumped isotopic composition of carbonates (denoted by Δ47). We restandardize and synthesize published data and report 159 new measurements of 25 samples. We derive a composite freshwater calibration and also evaluate differences in the Δ47-temperature dependence for different types of materials to examine whether material-specific calibrations may be justified. When material type is considered, there is a convergence of slopes between biological carbonates (freshwater gastropods and bivalves), micrite, biologically-mediated carbonates (microbialites and tufas), travertines, and other recently published syntheses, but statistically significant differences in intercepts between some materials, possibly due to seasonal biases, kinetic isotope effects, and/or varying degrees of biological influence. Δ47-based reconstructions of water δ18O generally yield values within 2‰ of measured water δ18O when using a material-specific calibration. We explore the implications of applying these new calibrations in reconstructing temperature in three case studies.

Insight into the causes of the West Antarctic Ice Sheet (WAIS) stability over middle Pleistocene glacial/interglacial (G/IG) cycles is fundamental to our understanding of the response of the climate system to the cryosphere. Here, to clarify the mechanism of WAIS stability during the late Quaternary period, we provide iceberg-rafted debris (IRD) contents, clay mineral, and Sr-Nd isotopic analyses of the piston core ANT34/A2-10. The core was recovered from the seasonal sea ice region in the Antarctic Zone of the Amundsen Sea with a ~773 ka BP chronology. The endmember analysis of clay minerals shows marked differences in sediment provenance at site ANT34/A2-10 between IRD peak interval and low IRD content interval in G/IG cycles. And the Sr-Nd isotopic endmember analysis in IRD peak intervals restricts the sediment provenance in the Victoria Land. We suggest that shifts in the sediment provenance resulted from the variations in iceberg trajectories, which connected to the significant shifts in the atmospheric system at the IRD peak intervals. Moreover, a contemporaneous strengthened ocean-driven positive feedback occurred between the increased wind-driven upwelling of warm, well-ventilated Circumpolar Deep Water and the intense ice mass loss process (including iceberg calving and basal melting process) with the instability of the WAIS. Furthermore, our results reveal that the variation of WAIS stability is sensitive to the local summer insolation forcing. These pieces of evidence recorded in the pelagic South Pacific Southern Ocean may strongly reflect the significant variations in ocean-driven and orbital forcing on WAIS stability on the orbital scale.